1. Field of the Invention
This invention relates to a coating liquid used in methods for coating recorded images, to an image recording method using that coating liquid, and to a recordings recorded therewith.
2. Description of the Related Art
Conventionally, the method of coating a recorded image with a laminate film is practiced as a method for protecting the recorded image and enhancing the bond between the recorded image and the base material. With this method, however, because separate process steps are required for supplying the laminate film, coating, and pressure application and the like, the apparatus itself becomes complex. With further innovations needed to effect suitable coatings, in Japanese Patent Application Laid-Open No. S59-104974/1984 (published), an apparatus is proposed for effecting good and suitable laminate coatings by the new addition, to the process, of an apparatus for detecting laminate film layer displacement. With this, however, the apparatus becomes even larger and more complex.
Ink jet recording, on the other hand, is a method wherewith text or graphics are recorded on the surface of a recording medium by ejecting small droplets of ink from very small nozzles. The ink jet recording procedures being implemented in practice include a method wherewith electrical signals are converted to mechanical signals using an electrostriction transducer, and ink stored in a nozzle head portion is discharged intermittently and text or symbols are recorded on the surface of a recording medium, and a method wherewith a part extremely close to the portion ejecting the ink stored in the nozzle head portion is rapidly heated to generate bubbles, intermittent ejection is effected by the cubical expansion of those bubbles, and text or symbols are recorded on the surface of a recording medium.
The recording liquids used in ink jet recording are mostly water-based in the interest of safety and recording properties, with water soluble dyes frequently used in the coloring agents, as a result of which these suffer the shortcoming of exhibiting inferior light resistance and water resistance. For that reason, various studies have been done on the use of pigments for the coloring agents with the object of gaining light resistance and water resistance in the recordings. With conventional methods, however, the fixation of the pigments to the recording medium is inadequate, which results in problems such as the paper smudging when rubbed with a finger, or a recorded portion becoming unsightly if the recording is marked with a so-called magic marker. Another problem therewith is inadequate glossiness.
As a separate measure, providing a protective coating layer to recordings recorded with ink jet recording procedures has been proposed for some time as a method for improving water resistance, fixation, and glossiness. In Japanese Patent Application Laid-Open No. S62-101482/1907 (published), for example, a method for fusion-transferring a thermally fusing coating agent onto a recorded image is investigated as a method for imparting water resistance to recordings colored with water soluble dye inks. In Japanese Patent Application Laid-Open No. H1-141782/1989 (published) and Japanese Patent Application Laid-Open No. H2-80279/1990 (published), a method is proposed for applying a liquid containing an isocyanate compound to a recorded image, and hardening it, to form a protective coating layer. In Japanese Patent Application Laid-Open No. H6-115066/1994 (published), a method in proposed wherewith high-quality recordings exhibiting outstanding bonding can be effected by forming a transparent topcoat layer after recording with an ink jet recording procedure on an ink absorption layer. And in Japanese Patent Application Laid-Open No. H9-262971/1997 (published), a printer is proposed wherewith, by spraying and fixing a laminate agent for laminating the recorded surface of a recording medium, recordings are obtained which can stand up under outdoor use. When such methods are used, however, the laminating apparatus itself is complex, or a hardening and fixing process using heat or UV radiation is required when forming the topcoat layer, or a separate process step is required for applying the film under pressure.
From the perspective of recording light resistance and water resistance, moreover, when a pigment like carbon black or the like is used for the colorant, dispersion in the ink is poor, clogging occurs, and pigment agglomeration occurs during storage, wherefore various kinds of dispersants have been studied. However, when these various dispersants such, for example, as resin dispersants, are merely added, those dispersants induce dispersion by adsorbing to the surface of the pigment particles, but the dispersants become detached from the surface of the pigment particles due to some causative factor or other, wherefore satisfactory dispersing effects have not been obtained. In cases where penetrating agents are added into the ink composition to impart a strong penetrating effect in order to increase the recorded image drying speed, in particular, dispersion stability sometimes deteriorates even more, a phenomenon thought to be caused by dispersant detachment being thereby promoted.
Thereupon, so-called self-dispersing surface-treated pigments (hereinafter called xe2x80x9csurface-treated pigmentsxe2x80x9d) have been proposed which improve pigment dispersion by subjecting the pigment particles to a surface treatment and thereby make it possible to disperse and/or dissolve the pigment particles in water without a dispersant. In Japanese Patent Application Laid-Open No. H10-195360/1998 (published) and Japanese Patent Application Laid-Open No. H10 330665/1998 (published), for example, self-dispersing carbon black is disclosed wherein a hydrophilic group such as the carboxyl group, carbonyl group, sulfone group, or hydroxyl group is bonded to the surface of the carbon black, either directly or with another atom group intervening. In Japanese Patent Application Laid-Open No. H8-3498/1996 (published), Japanese Patent Application Laid-Open No. H10-195331/1998 (published), and Japanese Patent Application Laid-Open No. H10-237349/1998 (published), for example, subjecting the surface of carbon black to an oxidation treatment to improve dispersion properties is proposed. And in Japanese Patent Application Laid-Open No. H8-283598/1996 (published), Japanese Patent Application laid-Open No. H10-110110/1998 (published), and Japanese Patent Application Laid-Open No. H10-110111/1998 (published), for example, surface-treated pigments are proposed wherein sulfone groups are inducted to the surfaces of organic pigments.
By using such surface-treated pigments as these in inks, it is possible to reduce the contained quantities of dispersants such as the resin dispersants conventionally used, or to avoid using such altogether. As a consequence, the solid matter content in ink compositions can be reduced, wherefore the viscosity of ink compositions can be lowered, the occurrence of clogging suppressed, and limitations on additives relaxed. Thus it is known that surfactants can be added to make fast-drying inks that penetrate faster into the recording medium, that the pigment content can be increased by the measure that the dispersant content can be reduced, and that, therefore, high image quality can be achieved with enhanced coloration.
Nevertheless, although it is possible to raise the image density on the recording medium and obtain high picture quality by increasing the pigment content in inks, new problems have arisen in that fixation or rubbing resistance deteriorates. Such decline in fixation and/or rubbing resistance is particularly conspicuous in glossy recording mediums having smooth surfaces.
Thereupon, an object of the present invention is to provide a coating liquid that does not require hardening or fixing processes using heat or UV radiation or the like, and also a recording method that, by coating that coating liquid with an ink jet recording procedure, imparts recording fastness in terms of light resistance, water resistance, and fixation, etc., and good image quality with outstanding glossiness, together with recordings recorded thereby.
Another object of the present invention is to provide a recording method wherein that coating liquid is used, wherewith, by using a surface-treated pigment as the pigment, recording can be performed with high image density and high picture quality, exhibiting rapid drying in addition to the proportion noted above, and wherewith fixation and rubbing resistance can be improved, together with recordings recorded thereby.
The inventors, as a result of intense investigations in an effort to resolve the problems noted in the foregoing, discovered that by controlling the penetrability of the coating liquid, recorded images are dried and fixed without requiring processes such as heating or hardening after coating on the coating liquid, and that recorded images exhibiting outstanding light resistance, water resistance, fixation, and image glossiness are thereby obtained, and thus have come to propose the present invention.
The present invention, specifically, is a coating liquid for application to recorded images containing at least water, fine polymer particles, and a penetrating agent. By providing this coating liquid, an object or objects noted earlier are attained.
The present invention also provides the coating liquid noted above wherein the surface tension in that coating liquid at 20xc2x0 C. is 40 mN/m.
The present invention is the coating liquid described above, wherein the penetrating agent is one or more substances selected from a group consisting of an acetylene glycol surfactant, an acetylene alcohol surfactant, a glycol ether, and a 1,2-alkylene glycol.
The present invention also provides the coating liquid described above, wherein the penetrating agent is an acetylene glycol surfactant and/or an acetylene alcohol surfactant, such acetylene glycol surfactant is one to which on average 30 or fewer ethylene oxy groups and/or propylene oxy groups are added to 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimetyl-4-octine-3,6-diol, or 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octine-3,6-diol, and such acetylene alcohol surfactant is one to which on average 30 or fewer ethylene oxy groups and/or propylene oxy groups are added to 2,4-dimethyl-5-hexine-3-ol or 2,4-dimethyl-5-hexine-3-ol.
The present invention also provides the coating liquid described above, wherein the penetrating agent is a glycol ether, and that glycol ether is ethylene glycol mono(alkyl having 4 to 8 carbons) ether, triethylene glycol mono(alkyl having 4 to 8 carbons) ether, propylene glycol mono(alkyl having 3 to 6 carbons), or dipropylene glycol mono(alkyl having 3 to 6 carbons) ether.
The present invention also provides the coating liquid described above, wherein the penetrating agent is a 1,2-alkylene glycol, and that 1,2-alkylene glycol is a 1,2-(alkyl having 4 to 10 carbons) diol.
The present invention also provides the coating liquid described above, wherein the amount of the fine polymer particles contained is within a range of 1 to 40 wt. %.
The present invention also provides the coating liquid described above, wherein the minimum film formation temperature for the fine polymer particles is room temperature.
The present invention also provides the coating liquid described above, wherein the fine polymer particles are used as an aqueous emulsion configured only of a resin or resins having an acid value of 100 or less.
The present invention also provides the coating liquid described above, wherein the penetrating agent is an ethylene glycol surfactant and/or acetylene alcohol surfactant contained in an amount of 0.1 to 5.0 wt. %.
The present invention also provides the coating liquid described above, wherein the penetrating agent is a glycol ether contained in an amount of 0.5 to 30 wt. %.
The present invention also provides the coating liquid described above, wherein the penetrating agent is a 1,2-acetylene glycol contained in an amount of 0.5 to 30 wt. %.
The present invention also provides the coating liquid described above, containing at least one substance having the structure represented in formula (I) below.
R-EOn-POm-Xxe2x80x83xe2x80x83(I) 
(where R represents an alkyl group having 1 to 12 carbons, the structure whereof may be either a straight chain or branching; X represents xe2x80x94H or xe2x80x94SO3M (where M is a counter ion that is hydrogen ion, alkaline metal ion, ammonium ion, or organic ammonium ion); EO represents an ethylene oxy group; PO represents a propylene oxy group; and n and m are repeating units, indicating mean values in one of the substances expressed in formula (I). EO and PO indicate presence in the molecule, with the order thereof being irrelevant.)
The present invention also provides the coating liquid described above, wherein R indicated in formula (I) above is an alkyl group having 4 to 10 carbons.
The present invention also provides the coating liquid described above, wherein the substance expressed in formula (I) above is one wherein R is a butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, or decyl group.
The present invention also provides the coating liquid described above, wherein the substance expressed in formula (I) above has as its main component at least one substance expressed in formula (I) wherein R is a butyl group selected from among the n-butyl, isobutyl, and t-butyl groups, or has as its main component at least one substance expressed in formula (I) wherein R is a pentyl group selected from among the n-pentyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is a hexyl group selected from among the n-hexyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is a heptyl group selected from among the n-heptyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is an octyl group selected from among the n-octyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is a nonyl group selected from among the n-nonyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is a decyl group selected from among the n-decyl group and other isomers.
The present invention also provides the coating liquid described above, wherein the substance expressed in formula (I) above is one wherein n is 0 to 10, and m is 1 to 5.
The present invention also provides the coating liquid described above, wherein the substance expressed in formula (I) above has an average molecular weight of 2,000 or less.
The present invention also provides the coating liquid described above, wherein the substance expressed in formula (I) above is contained in an amount of 0.5 to 30 wt. %.
The present invention also attains an object or objects noted earlier by providing an image recording method wherein the coating liquid described above is discharged onto at least the image portion of a recording medium using an ink jet head to form a coating.
The present invention also provides the image recording method described above, wherein the image to which the coat is applied was formed by discharging an ink composition onto a recording medium using an ink jet head.
The present invention also provides the image recording method described above, wherein the ink composition contains at least water, a colorant, and a penetrating agent.
The present invention also provides the image recording method described above wherein the colorant is a dye.
The present invention also provides the image recording method described above wherein the colorant is a pigment.
The present invention also provides the image recording method described above wherein the pigment is made one that is capable of being dispersed and/or dissolved in water by a dispersant.
The present invention also provides the image recording method described above wherein the pigment is surface-treated so that at least one of the functional groups represented below, or salt thereof, is bonded either directly or with a polyvalent group intervening, to the surface thereof, and is made capable of being dispersed and/or dissolved in water without a dispersant;
xe2x80x94OM, xe2x80x94COOM, xe2x80x94COxe2x80x94, xe2x80x94SO3M, xe2x80x94SO2NH2, xe2x80x94RSO2M, xe2x80x94PO3HM, xe2x80x94PO3M2, xe2x80x94SO2NHCOR, xe2x80x94NH3, xe2x80x94NR3 (where M is a hydrogen atom, alkaline metal, ammonium, or organic ammonium, and R is an alkyl group having 1 to 12 carbons, a phenyl group that may have a substituent group, or a naphthyl group that may have a substituent group).
The image recording method described above, wherein the polyvalent group is an alkyl group, a phenyl group that may have a substituent group, or a naphthyl group that may have a substituent group, having 1 to 12 carbons.
The present invention also provides the image recording method described above wherein the pigment is surface treated with a treatment agent containing sulfur so that SO3M and/or xe2x80x94RSO2M (where M is a counter ion that is a hydrogen ion, alkaline metal ion, an ammonium ion, or an organic ammonium ion) is chemically bonded to the surface of the particles thereof, and made capable of dispersing and/or dissolving in water.
The present invention also provides the image recording method described above, wherein the liquid in which the surface-treated pigment is dispersed exhibits a zeta potential having an absolute value of 30 mv or greater at 20xc2x0 C. and pH 8 to 9.
The present invention also provides the image recording method described above wherein the surface tension of the ink composition at 20 C. is 40 mN/m or less.
The present invention also provides the image recording method described above wherein the penetrating agent is one or more substance selected from among a group comprising acetylene glycol surfactants, acetylene alcohol surfactants, glycol ethers, and 1,2-alkylene glycols.
The present invention also provides the image recording method described above wherein the penetrating agent is an acetylene glycol surfactant and/or an acetylene alcohol surfactant, such acetylene glycol surfactant is one to which on average 30 or fewer ethylene oxy groups and/or propylene oxy groups are added to 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimetyl 4-octine-3,6-diol, or 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octine-3,6-diol, and such acetylene alcohol surfactant is one to which on average 30 or fewer ethylene oxy groups and/or propylene oxy groups are added to 2,4-dimethyl-5-hexine-3-ol or 2,4-dimethyl-5-hexine-3-ol.
The present invention also provides the image recording method described above, wherein the penetrating agent is a glycol ether, and that glycol ether is ethylene glycol mono(alkyl having 4 to 8 carbons) ether, triethylene glycol mono(alkyl having 4 to 8 carbons) ether, propylene glycol mono(alkyl having 3 to 6 carbons), or dipropylene glycol mono(alkyl having 3 to 6 carbons) ether.
The present invention also provides the image recording method described above, wherein the penetrating agent is a 1,2-alkylene glycol, and that 1,2-alkylene glycol is a 1,2-(alkyl having 4 to 10 carbons) diol.
The present invention also provides the image recording method described above wherein the penetrating agent is an acetylene glycol surfactant of acetylene alcohol surfactant the contained amount whereof is 0.1 to 3.0 wt. %.
The present invention also provides the image recording method described above wherein the penetrating agent is a glycol ether, the contained amount whereof is 0.5 to 30 wt. %.
The present invention also provides the image recording method described above wherein the penetrating agent is a 1,2-alkylene glycol the contained amount whereof is 0.5 to 30 wt. %.
The present invention also provides the image recording method described above wherein at least one substance having the structure represented by formula (I) below is contained in the ink composition:
R-EOn-POm-Xxe2x80x83xe2x80x83(I) 
(where R is an alkyl group having 1 to 12 carbons, the structure whereof is a straight chain or branched structure, X is xe2x80x94H or SO3M (where M is a counter ion that is a hydrogen ion, alkaline metal ion, ammonium ion, or organic ammonium ion), EO is an ethylene oxy group, PO is a propylene oxy group, and n and m are repeating units, representing mean values in one of the substances expressed in formula (I). EO and PO indicate presence in the molecule, with the order thereof being irrelevant.)
The present invention also provides the image recording method described above wherein the R in the formula (I) is an alkyl group having 4 to 10 carbons.
The present invention also provides the image recording method described above wherein, in the substance expressed by the formula (I), R is a butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, or decyl group.
The present invention also provides the image recording method described above wherein the substance expressed in formula (I) above has as its main component at least one substance expressed in formula (I) wherein R is a butyl group selected from among the n-butyl, isobutyl, and t-butyl groups, or has as its main component at least one substance expressed in formula (I) wherein R is a pentyl group selected from among the n-pentyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is a hexyl group selected from among the n-hexyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is a heptyl group selected from among the n-heptyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is an octyl group selected from among the n-octyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is a nonyl group selected from among the n-nonyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is a decyl group selected from among the n-decyl group and other isomers.
The present invention also provides the image recording method described above, wherein the substance expressed in formula (I) above is one wherein n is 0 to 10, and m is 1 to 5.
The present invention also provides the image recording method described above, wherein the substance expressed in formula (I) above has an average molecular weight of 2,000 or less.
The present invention also provides the image recording method described above, wherein the substance expressed in formula (I) above is contained in an amount at 0.5 to 30 wt. %.
The present invention also provides a recording recorded by the image recording method described above.
Detailed descriptions are now given of the coating liquid, image recording method, and recordings of the present invention.
(Coating Liquid)
The coating liquid of the present invention comprises at least water, fine polymer particles, and a penetrating agent, particularly one or more penetrating agents selected from a group made up of acetylene glycol surfactants, acetylene alcohol surfactants, glycol ethers, and 1,2-alkylene glycols.
By fine polymer particles here is meant resins in general. That is, water soluble resins, and water insoluble resins dispersed in a fine particle form in water (generally expressed as emulsions, dispersions, latexes, or suspensions) in general.
For the fine polymer particles that can be used in the coating liquid of the present invention, it is possible to use anything so long as it will stably dissolve and/or disperse in water. The weight average molecular weight thereof should be within a range of 2,000 to 300,000 with 3,000 to 100,000 being a preferable range. If the weight average molecular weight is too low, image protection will cease to be adequate. If the weight average molecular weight is too high, the viscosity will be too high for coating with an ink jet recording procedure and it will be difficult to use.
Examples of such fine polymer particles include polyacrylic acids, styrene-acrylic acid compolymers, styrene-acrylic acid-acrylic acid alkyl ester copolymers, styrene-maleic acid copolymers, styrene-maleic acid-acrylic acid alkyl ester copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylic acid alkyl ester copolymers, and styrene-maleic acid-half ester copolymers, together with salts thereof.
Also, the fine polymer particles contained in the coating liquid of the present invention may be used as an aqueous emulsion. This aqueous emulsion should be one the continuous phase whereof is water, and the dispersion phase whereof is an acrylic resin, methacrylic resin, styrene resin, urethane resin, acrylamide resin, epoxy resin, or mixture thereof. It is particularly desirable that the dispersion phase consist of acrylic acid and/or methacrylic acid. For the aqueous emulsion used in the coating liquid of the present invention, one consisting of the fine polymer particles noted earlier can be used, but it is particularly desirable that it exhibit film forming properties, with a minimum film formation temperature that is at or below room temperature (but minus 10xc2x0 C. or greater) at the location where the printer is used, and preferably a temperature no less than 0xc2x0 C. and no greater than 20xc2x0 C. When the minimum film formation temperature is within this temperature range, there is no need to separately employ a special heating apparatus when forming the coating layer, thereby making it possible to make the image recording apparatus smaller and lighter in weight, with another benefit being that operation in not onerous during image formation.
By the fine polymer particles xe2x80x9cexhibiting film formation propertiesxe2x80x9d is here meant that the fine polymer particles have the capability of forming a coating film, when maintained at or above the minimum film formation temperature thereof, by the fine particles uniting and fusing together. Accordingly, when fine polymer particles having film forming properties are used, the fine polymer particles fuse and join together on the recording medium so that a coating film is formed. As a result, the rubbing resistance, water resistance, and glossiness of the recording can be greatly improved.
The fine polymer particles described in the foregoing is particularly well suited for use as an aqueous emulsion configured solely of a resin or resins having an acid value of 100 or less. When the acid value of the resin in the aqueous emulsion is 100 or lower, the resin will be substantially insoluble in water and, as a consequence, a coating layer formed solely therefrom will also be insoluble in water. Accordingly, in images whereon a coating layer is formed, even when a dye is used as the colorant, a benefit is gained in that recordings are obtained which exhibit good water resistance. Specific examples of such aqueous emulsions that can be cited include the Joncryl emulsions J-390, J-711, J-511, J-7001, J-632, J-741, J-450, J-840, J-47J, J-734, J-7600, J-775, J-537, J-352, J-790, J-780, and J-1535 (these being the names of products made by Johnson Polymer Co., Ltd.), Primal E-2212, Primal I-62, Primal I-94, Primal I-98, and Primal I-100 (products produced by Rohm and Haas Co.), etc., all of which are commercially available and usable as they are.
The amount of such fine polymer particles contained in the coating liquids of the present invention need only be such as both to enable images on recording mediums to be thoroughly coated when sprayed with an ink jet recording procedure and to cause no problems such as nozzle clogging when performing ink jet recording, with 1 to 40 wt. % in the coating liquid being a suitable amount, but preferably 2 to 20 wt. %, and more preferably 4 to 15 wt. %. When the fine polymer particles are used as an aqueous emulsion, the cited addition amounts correspond to the amounts of the solid resin part.
The surface tension of the coating liquids in the present invention should be 40 mN/m or less at 20xc2x0 C. By making the surface tension 40 mN/m or lower, it is possible to form more uniform coating layers.
The coating liquids of the present invention should contain penetrating agents consisting of acetylene glycol or acetylene alcohol surfactants. By adding such penetrating agents as these, penetration into the recording medium is enhanced, and coating liquid fixation is also enhanced, which are benefits.
Citable examples of acetylene glycol surfactants include those wherein an average 30 or fewer ethylene oxy groups and/or propylene oxy groups are added to 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimetyl-4-octine-3,6-diol, or 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octine-3,6-diol, and citable examples of acetylene alcohol surfactants include those wherein on average 30 or fewer ethylene oxy groups and/or propylene oxy groups are added to 2,4-dimethyl-5-hexine-3-ol, 3,5-dimethyl-1-hexane-3-ol, or, alternatively, 2,4-dimethyl-5-hexine 3 ol, 3,5-dimethyl-1-hexane-3-ol.
Particularly preferable among these are 2,4,7,9-tetramethyl-5-dicine-4,7,-diol, 3,6-dimethyl-4-octine-3,6-diol, and 3,5-dimethyl-1-hexane-3-ol.
It is also possible to use commercially available products for the acetylene glycol surfactant, specific examples whereof include Surfynol 82, 104, 240, 465, 485, and TG (all available from Air Products Co.), and a specific example of an acetylene alcohol surfactant is Surfynol 61 (also available from Air Products Co.).
The amount of the acetylene glycol surfactant and/or acetylene alcohol surfactant added to the coating liquid of the present invention should be 0.1 to 5.0 wt. % relative to the total volume of coating liquid, with a range of 0.5 to 2 wt. % being more favorable. When the amount added is within this range, the penetration-induced fixation of the coating liquid improves even further, and continuous high-speed coating is made easier.
The coating liquid of the present invention should also contain a penetrating agent selected from among glycol ethers and 1,2-alkylene glycols. By adding these penetrating agents, penetration into the recording medium is enhanced, and coating liquid fixation is also enhanced, which are benefits. These penetrating agents also act to enhance the film forming properties of the fine polymer particles described earlier, whereupon coating layers can be formed effectively on image surfaces.
The glycol ethers noted above should be one or a mixture of two or more substances selected from among a group comprising ethylene glycol mono(alkyl having 4 to 8 carbons) ether, triethylene glycol mono(alkyl having 4 to 8 carbons) ether, propylene glycol mono(alkyl having 3 to 6 carbons), and dipropylene glycol mono(alkyl having 3 to 6 carbons) ether.
Specific examples of glycol ethers, inclusive of glycol ethers other than those noted above, include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, triethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether, and dipropylene glycol mono-n-butyl ether.
For the 1,2-alkylene glycols noted earlier, moreover, 1,2-(alkyl having 4 to 10 carbons) diols are preferable, specific examples whereof include, as specific examples of 1,2-alkylene glycols, 1,2-pentanediol, and 1,2-hexanediol, etc.
The coating liquid of the present invention should also contain 0.5 to 30 wt. % of the glycol ethers and/or 1,2-alkylene glycols noted earlier, and preferably contain 3 to 30 wt. % thereof. When that amount is less than 0.5 wt. %, the effect of enhancing penetration into the recording medium diminishes and the coating liquid becomes difficult to fix. When that amount exceeds 30 wt. %, the viscosity of the coating liquid rises and it becomes difficult to use the coating liquid in coating with an ink jet recording procedure. An even more favorable range is 5 to 10 wt. %.
According to a preferable aspect of the coating liquid of the present invention, in view of the fact that some of the acetylene glycol surfactants and/or glycol ethers noted in the foregoing exhibit low solubility in water, it is preferable that that solubility be improved by adding components such as the following. Examples of components that can be added include highly water-soluble glycol ethers, thiodiglycol, 1,4-butane diol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexane diol, 1,6-hexane diol, propylene glycol, dipropylene glycol, tripropylene glycol or other diols or glycols, as well as surfactants and the like.
The coating liquid of the present invention should contain therein at least one substance expressed in formula (I) below.
R-EOn-POm-Xxe2x80x83xe2x80x83(I) 
(where R is an alkyl group having 1 to 12 carbons, the structure whereof is a straight chain or branched structure, x is xe2x80x94H or SO3M (where M is a counter ion that is a hydrogen ion, alkaline metal ion, ammonium ion, or organic ammonium ion), EO is an ethylene oxy group, PO is a propylene oxy group, and n and m are repeating units, representing mean values in the system overall. EO and PO indicate presence in the molecule, with the order thereof being irrelevant.)
In the present invention, moreover, those substances in the xe2x80x9csubstances expressed in formula (I)xe2x80x9d wherein R is the same (regardless of whether n, m, and X are the same or different) are treated as one type.
By adding substances having the structure expressed in formula (I), the ability of the coating liquid to penetrate into the recording medium is enhanced. As a consequence, coating layer fixation is also enhanced, making it easier to perform continuous coating at high speed.
It is preferable that the R expressed in formula (I) be an alkyl group having 4 to 10 carbons. If the number of carbons in R is 3 or fewer, the effect of enhancing penetration will decline.
More specifically, in the substances expressed in formula (I), R should be a group having the number of carbons C4 (butyl group), C5 (pentyl group), C6 (hexyl group), C7 (heptyl group), C8 (octyl group), C9 (nonyl group), or C10 (decyl group). When R is C3 (propyl group) or lower, the effect of enhancing penetrability declines.
According to a more preferable aspect, the number of carbons is 4 to 8, and even more preferably still, 4 to 6. The structure of R may be straight chain or a branched structure. However, when comparing substances having the same number of carbons, those having a branched structure will exhibit higher effectiveness in enhancing penetrability, and so are preferred.
In the coating liquid of the present invention, furthermore, the substance expressed in formula (I) above has as its main component at least one substance expressed in formula (I) wherein R is a butyl group selected from among the n-butyl, isobutyl, and t-butyl groups, or has as its main component at least one substance expressed in formula (I) wherein R is a pentyl group selected from among the n-pentyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is a hexyl group selected from among the n-hexyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is a heptyl group selected from among the n-heptyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is an octyl group selected from among the n-octyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is a nonyl group selected from among the n-nonyl group and other isomers, or has as its main component at least one substance expressed in formula (I) wherein R is a decyl group selected from among the n-decyl group and other isomers.
In the substances expressed in formula (I), when X is xe2x80x94SO3M (where M is a counter ion that is a hydrogen ion, alkaline metal ion, ammonium ion, or organic ammonium ion), the alkaline metal may be Li, Na, or K, and the organic ammonium may be alkyl ammonium, alkanol ammonium, for example, such, for example, as monomethyl ammonium, diethyl ammonium, tripropyl ammonium, monoethanol ammonium, diethanol ammonium, triethanol ammonium, monoisopropanol ammonium, tripropanol ammonium, N-isobutyl alcohol ammonium, N,N-dimethyl ethanol ammonium, N,N-diethyl ethanol ammonium, etc.
When X is hydrogen, if the molecular weight of R or PO is large compared to EO, the hydrophobic property of the substances expressed in formula (I) overall will increase, wherefore the solubility thereof in water will tend to decline. When X is xe2x80x94SO3M, on the other hand, solubility in water is readily obtainable.
In tho coating liquid of the present invention, moreover, in the substances expressed in formula (I), n should be within a range of 0 to 10, and m within a range of 1 to 5.
The average molecular weight of the substance expressed in formula (I) should be 2,000 or less. When the average molecular weight exceeds 2,000, effectiveness in enhancing penetrability declines. It is preferable that the upper limit in this range be 1,000, and even more preferable that it be 500.
The amount of the substances expressed in formula (I) added to the coating liquid is discretionary, but a range of 0.5 to 30 wt. % relative to the total quantity of coating liquid is preferable, with 2 to 15 wt. % being more preferable, and 5 to 13 wt. % more preferable still. When the added amount is less than 0.5 wt. %, the effect of enhancing penetration is weakened, so the effect of enhancing coating liquid fixation declines. When the added amount exceeds 30 wt. %, the viscosity of the coating liquid rises, making coating with an ink jet recording procedure difficult.
In the coating liquid of the present invention, in terms of the components thereof, furthermore, such additives as UV absorbing agents, preservatives, antioxidants, electrical conductivity adjusting agents, pH adjusting agents, viscosity adjusting agents, surface tension adjusting agents, and oxygen absorbents can be appropriately used.
(Image Recording Method and Recordings)
The image recording method according to the present invention is a method wherewith the coating liquid of the present invention, described in the foregoing, is coated on with an ink jet recording procedure. That ink jet recording procedure may be performed by any commonly known method. For this reason, an apparatus for supplying the film coated becomes unnecessary, and there is no particular necessity either of an apparatus for effecting fixation, due to the properties of the coating liquids of the present invention. In order to further enhance fixation and/or image recording speed, however, an apparatus or the like for accelerating fixation or drying by heating or the like after coating may be used.
Another feature of the recording method of the present intention is that the images coated are effected using an ink jet recording procedure. Thereby, the ink jet recording apparatus for forming the images and the ink jet recording apparatus for spraying the coating liquid can be integrated into the same apparatus, and the equipment overall can be reduced in size, but it is also permissible to use two ink jet recording apparatuses, one for image recording and one for coating, connected in series.
With the image recording method of the present invention, moreover, a dye can be used for the colorant in the ink jet recording ink composition for recording images on recording mediums. For the dye used here, the water-soluble dyes used conventionally in ink jet recording ink compositions can be used. Examples of water-soluble dyes that can be used include disperse dye in addition to acid dye, basic dye, and direct dye.
With the recording method of the present invention, moreover, a pigment can be used for the colorant in the ink jet recording ink composition for recording on recording mediums. For the pigment used here, the pigments used conventionally in ink jet recording ink compositions can be used. Inorganic pigments such as titanium oxide, iron oxide, or carbon black, for example, can be used. Such organic pigments as azo pigments (for example, azo lake, insoluble azo pigment, or condensed azo pigment, etc.), polycyclic pigments (for example, phthalocyanine pigment, quinacridone pigment, or thioindigo pigment, etc.), nitro pigment, nitrose pigment, or aniline black can also be used.
Specific examples of inorganic pigments for use in black ink compositions that can be cited include such carbon blacks as furnace black, lampblack, acetylene black, and channel black (C. I. pigment black 7), and also iron oxide pigments and the like.
For organic pigments used in black ink compositions, such black organic pigments as aniline black (C. I. pigment black 1) or the like can be used.
Citable examples of pigments for use in yellow ink compositions include C. I. pigment yellow 1 (Hansa yellow G), 2, 3 (Hansa yellow 10G), 4, 5 (Hansa yellow 5G), 6, 7, 10, 11, 12, 13, 14, 16, 17, 24 (flavanthrone yellow), 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108 (anthrapyrimidine yellow), 109, 110, 113, 117 (copper complex salt pigment), 120, 124, 128, 129, 133, 130 (quinophthalone), 139 (isoindolinone), 147, 151, 153 (nickel complex pigment), 154, 167, 172, and 180, etc.
Citable examples of pigments for use in magenta ink compositions include C. I. pigment red 1 (parared), 2, 3 (toluidine red), 4, 5, (1 TR Red), 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38 (pyrazolone red), 40, 41, 42, 88 (thioindigo), 112 (naphthol AS based), 114 (naphthol AS based), 122 (dimethyl quinacridone), 123, 144, 146, 149, 150, 166, 168 (anthroanthrone orange), 170 (naphthol AS based), 171, 175, 176, 177, 178, 179 (perylene maroon), 185, 187, 209 (dichloroquinacridone), 219, 224 (perylene based), 245 (naphthol AS based), or, alternatively, C. I. pigment violet 19 (quinacridone), 23 (dioxazine violet), 32, 33, 36, 38, 43, and 50, etc.
Citable examples of pigments for use in cyan ink compositions include C. I. pigment blue 15, 15:1, 15:2, 15:3, 16 (non-metallic phthalocyanine), 18 (alkali blue toner), 25, 60 (cerulean blue), 65 (violanthrone), and 66 (indigo), etc.
In addition, citable examples of organic pigments for use in color ink compositions other than magenta, cyan, or yellow ink compositions include: C. I. pigment green 7 (phthalocyanine green), 10 (green gold), 36, and 37; C. I. pigment brown 3, 5, 25, and 26; and C. I. pigment orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, and 63, etc.
For the pigments noted above, those which are considered soluble and/or dispersable in water using a dispersant can be used. Dispersants can be generally categorized as anionic surfactant, nonionic surfactant, cationic surfactant, amphoteric surfactant, and high-molecular surfactant. Any of these may be selected as a dispersant for use in the ink compositions used in the image recording method of the present invention.
For the pigments noted in the foregoing, furthermore, it is preferable that they be xe2x80x9csurface-treated pigments,xe2x80x9d that is, pigments which have been subjected to a physical or chemical surface treatment so that, by a functional group or salt thereof being grafted to the surface of the pigment particle, either directly or with an intervening polyvalent group, they are rendered dispersable and/or soluble in water without a dispersant.
The functional groups grafted to one pigment particle may be either one or a plurality of types. The type of functional group grafted, and the degree thereof, should be determined as appropriate, giving consideration to the dispersion stability in the ink, color density, and drying characteristics at the front surface of the ink jet head, etc.
Citable examples of functional groups include xe2x80x94OM, xe2x80x94COOM, xe2x80x94COxe2x80x94, SO3M, xe2x80x94SO2NH2, xe2x80x94RSO3M, xe2x80x94PO3HM, xe2x80x94PO3M2, xe2x80x94SO2NHCOR, xe2x80x94NH3, and xe2x80x94NR3 (where M is a hydrogen atom, alkaline metal, ammonium or organic ammonium, R is an alkyl group, a phenyl group that may have a substituent, or a naphthyl group that may have a substituent, having 1 to 12 carbons), etc.
Citable examples of polyvalent groups include alkylene groups, phenylene groups that may have a substituent, and naphthylene groups that may have a substituent, having 1 to 12 carbons.
It is preferable that the pigments noted in the foregoing be surface-treated with a treatment agent containing sulfur so that SO3M and/or xe2x80x94RSO2M (where M is a counter ion that is a hydrogen ion, alkaline metal ion, ammonium ion, or organic ammonium ion) chemically bonds to the surface of the particles thereof. It is preferable, in other words, that those pigments be made capable of dispersing and/or dissolving in water by first dispersing the pigment in a solvent that has no active protons, that is not reactive with sulfonic acid, and wherein the pigment is insoluble or very slightly soluble, and then surface-treating the pigment with either amide-sulfuric acid or a complex of sulfur trioxide and a tertiary amine so that xe2x80x94SO3M and/or xe2x80x94RSO2M chemically bonds to the surface of the particles thereof.
Various commonly known surface treatment means can be employed as the surface treatment means for grafting the functional groups or salts thereof noted in the foregoing to the surface of the pigment, either directly or with an intervening polyvalent group.
Citable examples thereof include means wherewith commercially available oxide carbon black is treated with a solution of sodium hypochlorite or ozone and the carbon black is subjected to a further oxidization treatment to make the surface thereof more hydrophilic (described in Japanese Patent Application Laid-Open No. H7-250578/1995 (published), Japanese Patent Application Laid-Open No. H8-3498/1996 (published), Japanese Patent Application Laid-Open No. H10-120958/1998 (published), Japanese Patent Application Laid Open No. H10-195331/1998 (published), and Japanese Patent Application Laid-Open No. H10-237349/1998 (published), for example), means wherewith carbon black is treated with 3-amine-N-alkyl substituted pyridium bromide (described in Japanese Patent Application Laid-Open No. H10-195360/1998 (published) and Japanese Patent Application Laid-Open No. H10-330665/1998 (published), for example), means wherewith the organic pigment is dispersed in a solvent wherein that organic pigment is insoluble or slightly soluble and sulfone groups are inducted to the pigment particle surface using a sulfonating agent (described in Japanese Patent Application Laid-Open No. H8-283596/1996 (published), Japanese Patent Application Laid-Open No. H10 110110/1998 (published), and Japanese Patent Application Laid-Open No. H10-110111/1988 (published), for example), and means wherewith the organic pigment is dispersed in an alkaline solvent that forms a complex with sulfur trioxide, the surface of the organic pigment is treated by adding sulfur trioxide thereto, and sulfone groups or sulfonamine groups are inducted thereto (described in Japanese Patent Application Laid-Open No. H10-110114/1998 (published), for example). However, the fabrication means for the surface-treated pigments used in the present invention are not limited to or by these means.
The absolute value of the zeta potential of the surface-treated pigment dispersion liquid (aqueous dispersion liquid) used in the ink compositions of the present invention at 20xc2x0 C. and pH 8 to 9 should be 30 mV or higher. That is, because these surface-treated pigments secure dispersion stability by electrical repulsion induced by dispersed groups inducted to the surface of the particles thereof, it is preferable that the potential (zeta potential) at the pigment surface be at or above a certain value. In cases where the penetrating agents described subsequently and the surface-treated pigments described in the foregoing and deemed desirable in the ink compositions of the present invention are added to the ink composition, the absolute value of the zeta potential of the surface-treated pigment dispersion liquid at 20xc2x0 C. and pH 8 to 9 should be 30 mV or higher in order to secure pigment dispersion stability.
The zeta potential of the surface-treated pigment dispersion liquid at 20xc2x0 C. and pH 8 to 9 is measured with a laser Doppler electrophoresis apparatus (ELS-800 produced by Otsuka Electronic).
Surface-treated pigment dispersion liquids exhibiting zeta potential absolute values of 30 mV or higher at 20xc2x0 C. and pH 8 to 9 are obtained by such means as are described subsequently in example, for example.
The amount of pigment added as colorant, although discretionary, should be 0.5 to 20 wt. % relative to the total quantity of ink composition, with a range of 2 to 10 wt. % being preferable. At 0.5 wt. % and above, images having the desired image density are readily obtained, and, at 20 wt. % and below, the ink viscosity can be easily adjusted to facilitate stable discharge in ink jet procedures.
In the ink compositions used in the image recording method of the present invention, it is preferable that one or more substances selected from a group comprising acetylene glycol surfactants, acetylene alcohol surfactants, glycol ethers, and 1,2-alkylene glycols be used as the penetrating agent described earlier.
It is preferable that the acetylene glycol surfactants and acetylene alcohol surfactants used be the same as or similar to those used preferably in the coating liquid described earlier. The amount of each acetylene glycol surfactant and/or acetylene alcohol surfactant added should be 0.1 to 3 wt. % relative to the total quantity of ink composition, with a range of 0.5 to 2 wt. % being preferable. When that amount is less than 0.1 wt. %, it is difficult to obtain an adequate penetration effect, and when 3 wt. % is exceeded, the nozzle surfaces on the ink jet head are wetted, and in some cases it is difficult to obtain stable discharge.
It is preferable that the glycol ethers and 1,2-alkylene glycols used be the same as or similar to those used preferably in the coating liquid described earlier. The amount of such glycol ethers and/or 1,2 alkylene glycols added should constitute a content of 0.5 to 30 wt. % relative to the entire quantity of ink composition, with a content ranging from 3 to 30 wt. % being preferable. When that amount is less than 0.5 wt. %, an adequate penetration effect is difficult to obtain. When 30 wt. % is exceeded, the viscosity of the ink composition rises, and in some cases it is difficult to obtain stable discharge.
The ink composition used in the image recording method of the present invention should also contain at least one substance having the structure expressed in formula (I) below in the ink composition.
R-EOn-POm-Xxe2x80x83xe2x80x83(I) 
(where R represents an alkyl group having 1 to 12 carbons, the structure whereof may be either a straight chain or branching; X represents xe2x80x94H or xe2x80x94SO2M (where M is a counter ion that is a hydrogen ion, alkaline metal ion, ammonium ion, or organic ammonium ion); EO represents an ethylene oxy group; PO represents a propylene oxy group; and n and m are repeating units, indicating average values in the system overall. EO and PO indicate presence in the molecule, with the order thereof being irrelevant.)
By adding substances having the structure expressed by the formula (I) above, the ink composition penetrability into the recording medium is enhanced. As to specific examples of substances such as these, substances the same as or similar to those used preferably in the coating liquid described earlier should be used.
The amount of the substances exhibited by formula (I) above added into the ink composition is discretionary, but should be 0.5 to 30 wt. % relative to the entire quantity of ink composition. When the added amount is less than 0.5 wt. %, the affect of enhancing penetrability is weakened, whereas when the added amount exceeds 30 wt. %, the viscosity of the ink composition rises and in some cases it is difficult to obtain stable discharge.
The surface tension of the ink composition used in the image recording method of the present invention should be 40 mN/m or less at 20xc2x0 C.
As components in the ink composition used in the image recording method of the present invention, furthermore, such additives as UV absorbing agents, preservatives, antioxidants, electrical conductivity adjusting agents, pH adjusting agents, viscosity adjusting agents, surface tension adjusting agents, and oxygen absorbents can be appropriately used.
In the image recording method of the present invention, moreover, the film thickness of the dried coating layer need only be such that the recorded images can be thoroughly coated, with 0.1 to 100 xcexcm being reasonable, and a range of 0.5 to 20 xcexcm being preferable. When the colorant in the image recording ink composition is a dye, a range of 2 to 20 xcexcm is to be preferred. When the colorant in the image recording ink composition is one made dispersable and/or soluble in water by a dispersant, a film thickness range of 0.5 to 5 xcexcm is to be preferred. And when the colorant in the image recording ink composition is a surface-treated pigment, a film thickness range of 0.5 to 10 xcexcm is to be preferred.
Paper is generally used for the recording medium used in the image recording method of the present invention, but a resin such as plastic or a metal or the like may also be used if the surface thereof has been treated and it has an ink absorption layer.
Recordings recorded using the image recording method of the present invention exhibit good recording fastness properties such as light resistance, water resistance, and fixation, and good image quality having outstanding glossiness is obtained, making them effective for use in outdoor posters and signs.
When a surface-treated pigment is used as the colorant in the image recording ink composition, in particular, in addition to the qualities noted above, the composition is fast-drying, making it possible to perform recording with high image density and high picture quality, and rubbing resistance can also be improved. Thus such image recording ink compositions are particularly effective for use in outdoor posters and signs.